Typically, crystalline propylene polymer materials, such as polypropylene and propylene polymer based copolymers, have found extensive use in various formed articles, such as injection-molded articles, blow-molded articles, films, sheets and fibers, because of their excellent mechanical properties. However, due to their nature, crystalline propylene polymer materials have the problem of being poor in transparency. To improve the transparency of polyolefins, nucleating or clarifying agents are generally incorporated therein such as described in U.S. Pat. No. 4,388,119 which discloses a composition consisting essentially of a solid powdery dibenzylidene sorbitol coated with a higher fatty acid.
U.S. Pat. No. 5,001,179 discloses the use of a dibenzylidene sorbitol based compound and a cyclodextrin in a crystalline polyolefin type composition to obtain transparency and odor-non-emitting properties.
While incorporating the sorbitol based compounds in polyolefin resins improves the transparency of the polyolefin resin, high processing temperatures must be used in order to melt and properly disperse the sorbitol-based compound which have melting points of at least 220.degree. C.
Low processing temperatures are preferred in the industry to prevent the degradation or decomposition of the propylene polymer material. However, at lower processing temperatures white specks of unmelted and poorly dispersed sorbitol-based compounds are found in the resulting molded articles because the processing temperature is lower than the melting points of the sorbitol based compounds. Thus, there is a desire to find clarifying agents which can be used at lower processing temperatures, without the problem of obtaining white specks in the final product.